Speaker
Zhen LIU
(University of Science and Technology of China)
Description
Quarkonium production is an important tool to study the properties of the Quark-Gluon Plasma (QGP) formed in relativistic heavy-ion collisions. In particular, suppression of the J/ψ meson production due to the color screening effect in the medium was proposed as a direct evidence of the QGP formation. However, interpretation of the J/ψ suppression measured in heavy-ion collisions is still challenging due to the presence of other effects, such as the regeneration contribution from the coalescence of deconfined c and c quarks as well as the cold nuclear matter effects. By comparing J/ψ production cross-sections in p+p and p+Au collisions, the cold nuclear matter effects can be studied in detail. Moreover, J/ψ polarization is sensitive to the J/ψ production mechanism, and its measurement can help distinguish among different models. During the RHIC 2015 run, the STAR experiment recorded large samples of p+p and p+Au collisions at √sNN = 200 GeV for charmonium studies via the dimuon decay channel. In this talk, we will present measurements of the nuclear modification factor for J/ψ over a broad kinematic range in p+Au collisions, to quantify the cold nuclear matter effects. The double ratio of ψ(2S) to J/ψ production rates between p+p and p+Au collisions at mid-rapidity is measured for the first time, to study possible different final-state effects on different charmonium states. Furthermore, we will discuss the analysis status of J/ψ polarization measurements in both p+p and p+Au collisions.
